Joint development of bullying and victimization in adolescence: relations to delinquency and self-harm.

OBJECTIVE To estimate trajectories of bullying and victimization in early to mid-adolescence, associations between the trajectories, and links with delinquency and self-harm. METHOD A total of 3,932 adolescents (50% boys) reported bullying (ages 14 to 16), victimization (ages 13 to 16), delinquency (age 16), and self-harm (age 16). RESULTS Two bullying trajectories (low/decreasing, high/increasing) and three victimization trajectories (low, high/decreasing, high/increasing) were identified. Over time, victimization increased the likelihood of involvement in bullying to a greater extent than bullying increased the likelihood of victimization. Boys and girls in the high/increasing bullying and the low or high/increasing victimization trajectories (i.e., the bullies and the bully-victims) were highest in mid-adolescent delinquency. Girls following the high/increasing bullying and high/increasing victimization trajectories (bully-victims) were the highest in mid-adolescent self-harm. CONCLUSIONS Youths who are victimized by their peers are at increased risk, in turn, of victimizing others. Sex-specific adjustment problems are associated with differing patterns of involvement in bullying and victimization among adolescents.